I've written before about cell phones and the persistent fear that they damage your brain. The subject isn't a new one. But it's come up again because there was a meeting last month of a World Health Organization working group called the International Agency for Research on Cancer (IARC). After reviewing the current research, including the results of a study called Interphone, the group announced that they were classifying cell phones as "possibly carcinogenic to humans."

To be clear, the conclusion of that Interphone study was the following: "Overall, no increase in risk of [brain cancer] was observed with use of mobile phones."

But the authors do report "suggestions" that one type of brain tumor was more common among the group of people who reported spending the most hours on their cell phones. They point out, though, that there are problems with this finding.

The study relied on subjects' own recollections of how much time they spent on the phone--over a ten-year period. That would be enough of a challenge for a healthy person to recall, but brain tumor patients can have added problems with cognition and memory. And the greatest impediment to getting accurate results in a study like this is the question itself: Excuse me, brain tumor patient, but might you have used your cell phone a lot before you got that brain tumor? Surely every cancer patient is eager to find an explanation for his or her disease. The authors acknowledge that, in a previous study, brain cancer patients were more prone to overestimate their time on the phone.

So why is the IARC taking this result seriously?

To answer that, let's look at how serious this new classification actually is. The IARC classifies chemicals and other agents under a 5-category system: Carcinogenic to humans, probably carcinogenic, possibly carcinogenic, not classifiable, and "probably not" carcinogenic. Of the 941 agents they've assessed, 266 are in the same "possibly carcinogenic" category as cell phones will be. It means that research has been done on the subject, and the possibility of cancer has not been definitively ruled out. But while it's pretty easy to show that, say, tobacco causes lung cancer or solar radiation causes skin cancer, it's very, very hard to show definitively that something does not cause cancer. In fact, out of those 941 agents, only 1 is listed as "probably not carcinogenic." It's a chemical called caprolactam. Go ahead, let your kids roll around in it. It's safe. Probably.

Other agents in the "possibly carcinogenic" category, by the way, include pickled vegetables, magnetic fields, and being a carpenter.

So it's technically possible that your cell phone, or almost any other object or substance in your environment, is giving you cancer. But in the case of cell phones, there's no known way that they could cause cancer. All radiation is not the same. High-energy UV rays, for example, knock electrons off of atoms and damage your DNA, which can cause problems when your cells multiply, which can lead to cancerous growths. But cell phones emit low-energy, "non-ionizing" radio waves. Science knows of no way that this type of radiation could cause cancer.

If you still want to go back to your landline phone, go ahead. Just try not to worry too much. That could kill you.

Who's Inkfish?

Hi, I'm Elizabeth. I live near Boston and work as the editor of MUSE, a kids' science magazine that's not otherwise related to this blog. My writing has also appeared in National Geographic, Slate, and other publications. Read more here.